In recent years, a hybrid vehicle having an effective combination of an engine and a motor for driving has been put into practical use as an environmentally-friendly vehicle. Such a hybrid vehicle is equipped with a power storage unit for supplying electric power to the motor serving as a driving source. The power storage unit supplies electric power to the motor at the time of start-up and acceleration and the like of the vehicle for generating driving force while collecting the kinetic energy of the vehicle as electric power at a downward slope, during braking, and the like.
The above-described charging and discharging for the power storage unit are performed, for example, in consideration of the state of charge (SOC) of the power storage unit. By maintaining the SOC in the appropriate range, overcharging and overdischarging of the power storage unit can be prevented.
For example, Japanese Patent Laying-Open No. 2006-101674 (Patent Document 1) discloses a charge/discharge control apparatus of the secondary battery which limits the charge/discharge power based on the state of the secondary battery in order to maintain the SOC of the secondary battery constituting a power storage unit in the appropriate range. According to this document, the charge/discharge control apparatus of the secondary battery includes estimating means for estimating the temperature of the secondary battery, and limiting means for limiting the charge/discharge power of the secondary battery based on the estimated temperature of the secondary battery. Furthermore, the charge/discharge control apparatus of the secondary battery calculates the estimated temperature of the secondary battery based on the state of the secondary battery detected by the sensor, and, based on this estimated temperature, sets the limited electric power corresponding to the limit value of the electric power at the time when the secondary battery is charged or discharged. Based on this limited electric power, the charge/discharge control for the secondary battery is performed.    Patent Document 1: Japanese Patent Laying-Open No. 2006-101674